[WIP] Migrate main window to flexible layout and mvvm

[tboby]

What did you fix? (provide a description or issue closes statement)

This refactors the MainWindow to be easier to understand, maintain and test by adopting an MVVM architecture.

Not quite done yet, putting this up to help with #198

Contains new dependencies:

• Microsoft.Toolkit.Mvvm: A best in class set of MVVM classes (to replace the built-in INPC and provide a messenger)
• Microsoft.Xaml.Behaviors: A really useful set of XAML helpers that let you bind commands to old WPF controls that don't have commands

Considerations

• Does this contain a new dependency? [Yes]
• Have I run the linter? [Yes]
• Is is a bug fix, feature request, or enhancement? [Enhancement]

[PeterJeff]

Is there something I can do to assist with this?

[dimon222]

Is there something I can do to assist with this?

Resolution of conflict wouldn't hurt :)

[PeterJeff]

I can make an attempt, but it's unclear if the work was completed since it is in draft state + the comment in the opening which may be resolvable but may not compile due to diff decay.

I ran into a harder time trying to do that for #209

[tboby]

@PeterJeff I can't remember how far I got, but looking at the changes I made to the view I imagine I did most of what I intended to. The best way to test would be to just checkout the PR and see if the UI still works properly.

The big problem you'll run into is that I completely rewrote the view into a much easier to maintain form that is completely incompatible with any changes made to the UI since I started this. It might be easier to merge or recreate any UI changes in main since this last synced in this PR, as it should make the UI easier to manage.